Device for centering transit-instruments over physical points



{No Model.)

C. H. BRIGHTLY, H. M. FULLER 8: E. A. SINGER, Jr DEVICE FOR GENTERINGTRANSIT INSTRUMENTS OVER PHYSICAL POINTS. No. 515,815. Patented Mar. 6,1894.

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4 UNITED STATES- PATENT OFFICE.

CHARLES H. BRIGHVTLY, HERBERT MQFULLER, AND EDGAR A. SINGER, JR,

OF PHILADELPHIA, PENNSYLVANIA.

DEVICE FOR CENTERING TRANSIT-INSTRUMENTS OVER PHYSICAL POINTS.

SPECIFICATION formingpart of Letters Patent No. 515,815, dated March 6,1894.

I Application filed January 23, 1893- Serial No. 459i (N 1110561) To dZZwhom, it may concern:

Be-it know u that we, GHARLEsH. BRIGHTLY,

snow and useful Improvements in Methods of "and Devices for CenteringTransit-Instruments over Physical Points, of which the following. is aspecification.

Our invention relates toimprovements in devices for centering engineerstransitsor other instruments that have to be set up accurately over agiven physical point, and the object of our invention is to furnish adevice by means of which the instrument may be centered with absoluteaccuracy at any time.

Our invention and device for centering surveying instruments is adaptedfor use either globne or in connection with the usual plumbo Ourcentering device consists of a small telescope attached tangentially tothe edge of the upper part-01 revoluble plate of the instrument andmoving rotarily with this upper part or plate, and being capable of anin- 3 dependent movement upon trunnions radially to this upper part orplate. This small telescope is furnished with the usual cross wires andis also furnished with a tangent screw ,and attachments by means ofwhich it may be rotated on its bearings in orderto bring 'thepoint intoits line of sight. The instrument is centered by rotating its upperplate,

and by taking observations of the point through the small telescope intwo or more po- {sitions as hereinafter described.

In the accompanying drawings forming part of this specification and inwhich similar letters of reference indicate similar parts throughout theseveral views, Figure l, is a skeleton end elevation of the head of anengineers transit instrument having our centeringinstrument attached;Fig. 2, adetached front elevation of our centering attachment; Fig. 3, acentral sectional elevation of the springactu ated plunger and its casewhich acts against the end of the tangentscrew on our attachment; Fig.4:, a plan, partly in section, of the lower parallel plate of theinstrument and the ball socket in which the ball attached to the upperpart of the instrument works; Fig. 5, a plan of rule used in connectionwith our centering attachment for rapidly center- 7 ing the instrument,and Fig. 6, a diagrammanner to any convenient part of the upper orrevoluble part of the instrument.

0, is a small telescope furnished with trunnions cl which are held byand free to turn in bearings in the frame a.

e is a tangent screw carried by frame a;

one end of this screw is furnished with a milled head e and the otherend engages one side of the projecting arm f from one of the trunnionsd.

g is a plunger (which is carried by frame a) the lower end of whichengages the arm f upon the side opposite from that of the'scr'ew e. Theupper part of this plunger passes through a case it which is suitablysecured to the frame a. 11 Fig. 3, is a collar or shoulder on thisplunger and j a spring, one end of which bears against this shoulder andthe other against the top of the case h; this spring causes the plungerg to always bear against the upper part of arm f on the trunnions and tokeep this 85 arm firmly against the end of the screw 6. By means ofscrew 2, plunger g and arm f the telescope 0 may be rotated in itsbearings so as to bring the point over which the instrument is to be setinto the line of sight of this tele- 9o scope. ,k are the screws whichsupport the cross wires of this telescope, the arrangement of thesecross wires being precisely similar to that of the arrangement of thewires of the ordinary transit or level cross wires. cross wire ispreferably placed so as to be in a plane which will always pass throughthe vertical axis of the instrument; the other or horizontal wire isplaced directly at right angles to the first one.

In using our attachment the instrument may be approximately centered bymeans of One 95 the usual plumb-bob, or if thisbe notused, theinstrumentis ;set .up roughly ,over the point and leveled, the telescopec is now inclined to bear upon the point so thatthecross 5 wires cut it,the top plate of the instrument is now revolved, say one hundred and.twenty degrees, and another. observation upon .the

point is made through thetelescope c. .Ifzthe cross wires do not cut thecenter of the point,

7 1 the top plate B is moved s ast correctthe error, and when it isfound that the cross wires of the telescope will cut the center of thepoint at three positions about one hun- Hdred and twentydegreesapartfthe iristru I ment is then accurately centered overthepoint.

' While itis possibleto eentertheinstru ment bythe method aboyedescribedit is apt to takei orie t met an can a v eysbesmred.

'zo onaccount of thenumelfons obseryations that are ely. t ben es am;

In order to facilitate and hasten theopera-i tion of centeringwithouttheaid ofitheplumb 7 b w akd se of a r 9;,Fig-wh h yv 2 be divided bylinesas she -retina, a yinum-p pf u l r rts- A 1 h s ru i acedtup h ther und s u edin any s itab e nnem jt e s ake n t herrp ieet c ry athepoint over which the instrument is toibe can,

tered, jTherule',hayi lgbeenlplaced uponthef,

ground, say,,alongs i de the point and theina andeighty degrees andianother observation 5 upon the rule isitaken, saythatthe horizontal crosswire now corresponds with the line a 15 on the rule. The meanbet weenthe lines, 15 and 35, or the line 25, will therefore be a line whichpassesthrough the. vertical axis of theinstrume'nt, and, thetangentscrew e is turneduntil cross wire'k'of' thefltelescope 0 correspondswith line 25. A point seen at the intersectionof cross wires- 7c l willnow be directlyin the vertical axis of the instru- 5 5 ment. By thismethod, the telescope a may rapidly and accuratelybe directed sothatitsf crosswires will cut, a pointupon the ground or any otherplacebeneath the instrument, which will be'upon a line correspondingwith be the vertical axis of the instrument. The cross wires may be.made to cut. the given physical point by shifting the upper partof theinstrument upon the lower parallel plate D.

In order that the upper part of the instrument may he sh ifted with easeupon the lower parallel plate, and without loosening the leveling screws0, we place in the side of the lower parallel plate and in threadedholes in these sides screws E, which are furnished with milled headsrandfthe. ends :of which" engage the vedges of the shifting plate F-'Fig.5, which carries the socket G, in which is placed theball H which isattached to the upper part of the instrument. The screws E arepreferably four in number and are placed seen thatby loosening one setof screws and by setting upuponth-e opposite one the shifting plate Fand the whole upper part of the instrument may beimoved inanydireetiomde' diametrically opposite one another; It will be 7 sired,and v by this, means the. ,cross. wires of the telescope .j'c mayrapidly and accuratelybe brought to bear npon the jphysicalnpointl Itwill be noticed that;the.abovef means for moving the' shif ting plateand instrument would often; be v.useful where only the ordinaryiplumhbob,arrangement was .in' use. V

% Hav ing thus described our inventiom-we claim 1. Theiherein describeddevicefor'centering, a surveyors instrument over a physical point, andincombination with said instrument, a framesecured to the upper orrotat-V V able plate of saidinstrument, a telescopefurnishedfwith cross wiresandmounted in bearings carriedby said. frame and placedtan- Igentiallyto said rotatable plate mechanism byimeanjs of which saidtelescopemay be rockedin itsbearings, and a graduated scale I which maybe placedalongside said physical point. L

2. QAsa device-for. centering a transit instrument over. a physicalpoint and in combinationwith said transit, a frame secured to v theperiphery of. the upper or rotatable plate of the instrument, anauxiliary telescope furnlshedwlth cross wires and, mounted in bear:

by neansof which said telescope may be rockedin its bearingsin ordergtobringthe point into itsline of, sight.

3. The co'mbination witha transit instrumentof a frametsecuredto andcarried by the ,upper or rotatable plate ofthe instru-v ment, a smalltelescope furnished with cross wires and carriedgin bearings in saidframe which are placed tangentially to said upper or rotatable plate,and a tangent. screw for rockingsaid telescope in its bearings, all sub-I stantially as andfor the purposes. set-forth.

CHAS. H. BRIGHTLY,

HERBERT M, FULLER; EDGAR A. SINGER, J3.

Witnesses:

OHAs. SAXE}, J r., DAVID WEBER,

ings "carried in said frame, and mechanism

